1. Field of the Invention
This invention relates to NMR (nuclear magnetic resonance) spectrometers and, more particularly, to a novel lock system for maintaining or stabilizing a magnetic field at a constant strength.
2. Prior Art
The need and desirability of stabilizing the magnetic field used to polarize a sample in an NMR spectrometer is known in the prior art. It has been proposed to use a permanent magnet in conjunction with a field coil in which the current is varied so as to regulate the intensity of the magnetic field produced by the magnet. The amount of regulation is determined by using a control sample mixed with or placed in the vicinity of a test sample, and making a measurement of some characteristic of the control sample which characteristic is related to or affected by variations in the field intensity. Several characteristics are taught by the prior art. Most prior art designs used predominantly analog circuits throughout the lock system, and such circuits tend to be more expensive than digital circuits.